Willkommen bei Paraselene.de


0 Pages
Graphic: Symbol MemoPad.


Coloured Light Patches in the Strasbourg Cathedral

Small openings in the canopy of trees can produce elliptical or almost circular light patches on the ground. This happens because the sun is no point source and small openings between leaves act like a camera obscura, projecting the image onto the ground. Different factors influence the shape and size of the light patches. The patches are actually cone sections, depending on solar elevation. A high sun will produce an almost circular image on a flat ground. During a solar eclipse, the light patches will take on the shape of a sickle, depending on the degree of the  occultation of the sun.

The images below image show coloured light patches produced by a church window of the Strasbourg Cathedral. Note that all the patches are elliptical, while the window elements are not. This happens because the openings are too large and the distance of the projection screen is too large.

While the light patches on the image above are clearly elliptical, they look blurred on the image below. This happens because the distance to the window is shorter. Very close to the window they would have taken on the shape of the window elements.

Further reading: H. J. Schlichting: Sonnentaler fallen nicht vom Himmel. In: Der mathematische und naturwissenschaftliche Unterricht, 48/4, 1995, pp.199-207. H. J. Schlichting: Farbige Sonnentaler auf dem Wasser. In: Physik in unserer Zeit, 39/6, 2008, p.302. H. J. Schlichting: Sonnentaler - Abbilder der Sonne. In: Physik 43/4, 1994, pp.2-6.


Links to related articles:
Grafik: URL dieser Seite.
Permanent link:

nach oben